QUESTION:
AIX3.2.5 XLC 1.3
My customer wanted to allow application users (and other developers
related to the project) to pin text and data segments in memory
for reliable performance. Normally one would immediately use the
plock() function to do this, but for government security reasons
the suid approach was not acceptable.
Earlier the customer had tried writing plock into a small kernal
extension to make plock callable without the security exposure.
This did not work. Eventually we were able to find someone in
Austin who showed us the correct way to do this - and now it works.
The fix satisfies our needs, but there is concern for the future.
We have not found in the supplied documentation any overt mention
that one should be allowed to do this, let alone the correct way
to do this. If it was in the doc we would not have bothered Austin.
The developers want to recommend that we incorporate this technique
into the application design. Since they did not find an explicit
discussion of how to do this in the documentation they are afraid
this capability may be deemed "unsupported" from an IBM perspective
and could potentially go away someday as AIX evolves.
Are we wrong to assume this is unsupported? Is there a publication
that explicitly discusses writing plock as a kernal extension that
we are not aware of?
Thank you.
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A: The 'pinu' kernel service was designed to allow users to pin memory as
you have desired to do. The fact that it is documented in
InfoExplorer indicates that this service is supported. In fact, the
'AIX Version 3.1 Risc System/6000 As A Real-Time System' Manual
(GG24-3633-00) specifically documents the use of 'pinu' within a
kernel extension to allow non-root users the ability to pin memory.
The above manual contains complete sample code demonstrating the
memory pinning kernel extension on pages 219 and 220 in appendix A.
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This item was created from library item Q677439 FFPZT
Additional search words:
AUTO AUTOMATIC COMPILERS DEC94 EXTEND EXTENSION FFPZT FOUND IX
KERNAL LOCATE OZIBM OZNEW PLOCK RISCL RISCSYSTEM SOFTWARE SUPPORTED
WRITE WRITER WRITING
WWQA: ITEM: RTA000053704 ITEM: RTA000053704
Dated: 10/1996 Category: RISCL
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